1. Field of the Invention
The present invention relates to a light emitting device and a fabrication method thereof and a light emitting system using the same, and particularly, to a light emitting device of which construction can be simplified, size can become smaller, and efficiency of condensation and radiation can be improved, and a fabrication method thereof and a light emitting system using the same.
2. Description of the Conventional Art
In general, a light emitting element was used simply as a signal display device. Recently, the light emitting element has been actively researched as a light source having various wavelengths and energy of many systems. The light emitting elements which have been frequently used include a laser diode (LD) and a light emitting diode (LED). The LD is being used as a light source in a light communication field, while the LED is gradually being applied to various fields as a lighting device or a backlight of an LCD (Liquid Crystal Display) device as well as a general display device.
Especially, the LED can be driven by a relatively low voltage and achieve high energy efficiency, so as to obtain a low heat generation and prolonged life span. In addition, there have come up with techniques capable of allowing a white light which was hard to embody in the conventional art to have a high brightness by using the LED. As a result, the LED is expected as a significant technique to substitute most lighting devices which have currently used.
FIG. 1 is a sectional view showing a general light emitting diode (LED) 10. As shown in the drawing, a buffer layer 12, an n-contact layer 13, an activation layer 14, and a p-contact layer 15 are sequentially deposited on a transparent substrate 11 make of such as a sapphire, an n-GaAs, or the like, by a chemical vapor deposition method. A MESA etching is carried out such that the n-contact layer 13 is exposed by a lithography process and a dry/wet etching process. Thereafter, a current diffusion layer 16 which is constructed to facilitate a light transmission is deposited on the formed structure, and parts to form electrodes are patterned. Afterwards, a p-electrode 17 and an n-electrode 18 are formed, respectively, on the exposed p-contact layer 15 and the n-contact layer 13. Here, a p-cladding layer and an n-cladding layer may be further formed at upper and lower portions of the activation layer 14.
Such constructed LED emits light by applying a voltage to the p-electrode 17 and the n-electrode 18. Here, when the voltage is applied, a hole and an electron are injected into the p-electrode 17 and the n-electrode 18. The injected hole and electron are re-coupled in the activation layer 14, thereby discharging light to the exterior.
In the LED or the LD having the similar structure thereto, heat is generated when the light is discharged to the exterior. If this heat is accumulated in the element, it is disadvantageous to degrade characteristics of the element and shorten its life span. Therefore, sub-mounts and radiation plates are designed and used for the light emitting element such as the LED or LD used for an optical communication or lighting.
The LED, as the light emitting element having the structure shown in FIG. 1, is joined to a flat type sub-mount with an electrode, and accordingly an electrode pattern formed on the sub-mount is connected to an electrode of the LED using a wire bonding technique. Afterwards, when the radiation plate is further joined to the lower portion of the sub-mount, the heat generated from the light emitting element can be effectively discharged outwardly.
However, in a general flat type sub-mount, when a thickness of a substrate is reduced under a predetermined thickness, because the substrate physically becomes fragile, its thickness should be maintained more than a predetermined value. As a result, because the heat generated from the light emitting element is transferred to the radiation plate via the thick sub-mount so as to cause a degradation of the element. Moreover, because the light emitting element is joined to the flat type sub-mount, light is scattered so as to lower light focusing efficiency.
Recently, on the other hand, researches for increasing stability of the light emitting elements have recently been carried out. Especially, in the light emitting element applied to a certain equipment requiring reliability, a separate voltage regulating device is connected to the light emitting element in order to provide against inflow of static electricity or a surge voltage inward the electrode of the light emitting element, thereby constructing a light emitting element package. That is, when the static electricity or the surge voltage is inputted inward the electrode of the light emitting element, a transient current flows in the light emitting element, and accordingly a light emitting element system may be destroyed. As a result, the voltage regulating device such as a zener diode is connected to the light emitting element in parallel.
The zener diode is such a device using a zener breakdown. Here, in fabricating the diode, when an impurity is in a very high concentration, a width of a space charge region becomes narrower, and thusly a strong electric field is generated even in a reverse voltage. This generated strong electric field decomposes a shared combination of lattice into a plurality of free electrons and holes. As a result, the zener diode reduces resistance and allows a remarkable reverse current to flow without a change of voltage. Therefore, when the zener diode having a predetermined breakdown voltage is connected in parallel to the electrode of the light emitting element in a reverse direction, even if high static electricity or surge voltage flows inwardly in an instant, a stable voltage is maintained so as to remarkably relieve an impact on the light emitting element system.
However, in the conventional art, after joining the light emitting element to the flat type sub-mount and the radiation plate, the light emitting element is connected to a constant voltage element such as the zener diode through a separate wire bonding process so as to fabricate the light emitting element package, whereby it is difficult to construct the element, increase fabricating costs thereby, and lower a yield thereof.
Furthermore, when a light emitting device having the light emitting element therein is constructed, many numbers of constant voltage elements must be separately connected to the light emitting device. As a result, its structure becomes complicated and processes thereof get difficult, thereby resulting in increasing costs.